Dependency management with CLR Assemblies and Types: Relationships - Marco Dorantes' WebLog - Site Home

I keep in mind the following concepts when designing with .NET Framework assemblies and types; that is, when doing object-oriented design —an activity also known as dependency management, which is equal and the same for the most part.

Aggregation between two types occurs when Type B is the declared type of any member in the structure of Type A and the latter does not dispose the former’s instance; e.g. Type A aggregates Type B or Type A aggregates System.EventHandler:

class A
{
  private B b;
  public event System.EventHandler OnEvent;
}

Composition between two types occurs when Type B is the declared type of any member in the structure of Type A and the latter has the responsibility to dispose the former’s instance; e.g. Type A composes Type B:

class A : System.IDisposable
{
  private B b;

  public void Dispose()
  {
    b.Dispose();
  }
}

Using between two types occurs when Type B is the declared type of any parameter in any method signature or local variable in method implementations of Type A; e.g. Type A is using Type B:

class A
{
  public B ItsBObject
  {
    get
    {
      return GetBObject();
    }
  }
  public void ProcessB(B b) {}
  private B GetBObject() {}
  private void f()
  {
    B b=GetBObject();
  }
}

Instantiation between two types occurs when Type B is instantiated by Type A; this relationship denotes the specific operation by of which Type A creates Type B instances; e.g. Type A instantiates Type B:

class A
{
 public void f()
 {
   B b=new B();
 }
}